Abstract: A method of densifying a porous substrate with pyrolytic carbon includes loading the substrate into an oven, admitting a reaction gas mixture to the oven, extracting an effluent gas from the oven, and recycling components of the effluent gas into the reaction gas mixture. The reaction gas mixture contains a pyrolytic carbon precursor gas together with a vector gas. The effluent gas contains residual components of the reaction gas mixture together with reaction products, including hydrogen. The recycling is performed after eliminating heavy hydrocarbons contained in the effluent gas.

Abstract: One or more porous substrates for densification (10) are loaded into an oven (12) into which there is admitted a reaction gas containing a pyrolytic carbon precursor gas comprising at least one gaseous hydrocarbons CxHy in which x and y are integers and x is such that 1<x<6, together with a vector gas comprising at least one gas selected from methane and inert gases. Effluent gas containing residual components of the admitted gas together with reaction products, including hydrogen, is extracted from the oven and at least a fraction of a gas stream extracted from the effluent gas and containing pyrolytic carbon precursor reagent gas is recycled (circuit 80) into the reaction gas admitted into the oven, the recycling being performed after eliminating heavy hydrocarbons (treatment 40) contained in the effluent gas.

Abstract: A porous substrate having a concave inside face and an outside face is disposed in an enclosure, and reactive gas is introduced into the enclosure to densify the substrate. At least a portion of the gas is divided into two non-zero fractions. The first fraction of the gas is fed to the inside face of the substrate. The second fraction of the gas is fed to only the outside face of the substrate. Alternatively, the first fraction of the gas is fed via a tooling extending into an inside volume defined by the concave inside face of the substrate.

Abstract: The present invention provides a method of densifying porous structures by chemical vapor infiltration. In characteristic manner, said densification method is implemented using toluene as a precursor for carbon. Said toluene is generally used mixed with at least one carrier gas.

Abstract: Part of the flow of reactive gas admitted into the enclosure (10) is guided to the inside of the volume defined by a concave inside face of the or each hollow-shaped substrate (S1, S2, S3) so that said concave inside face is swept in full by a fraction of the total admitted gas flow.

Abstract: Between the start and the end of the chemical vapor infiltration process, filtration conditions are modified by causing at least one of the following infiltration parameters to vary: retention time of the gas, pressure, temperature, concentration of precursor in the gas, and concentration of dopant, if any, in the gas; thereby adapting infiltration conditions to changes in the porometry of the substrate in order to control the microstructure of the material deposited within the substrate, in particular in order to conserve a microstructure that is constant.

Abstract: The substrate (10) is placed in an enclosure (12) and is heated so as to establish a temperature gradient within the substrate such that the substrate has a temperature in its portions remote from its exposed surfaces that is greater than its temperature at said surfaces. A gas constituting a precursor of carbon and comprising at least one saturated or unsaturated hydrocarbon is admitted into the enclosure, with the formation of pyrolytic carbon be favored in the higher temperature portions of the substrate. The gas comprises a mixture containing at least one saturated or unsaturated hydrocarbon and hydrogen, and the substrate is heated in such a manner as to establish a temperature gradient within the substrate on either side of a temperature of 1500 K, with hydrogen having an inhibiting role at temperatures below 1500 K.

Abstract: The substrate (10) is placed in an enclosure (12) and is heated so as to establish therein a temperature gradient such that the substrate has a higher temperature in portions that are remote from its exposed surfaces than at its exposed surfaces. A reaction gas constituting a precursor for the material to be infiltrated is admitted into the enclosure, with formation of the material being enhanced in those portions of the substrate that are at higher temperature. At the beginning of the infiltration process, and at least during the major portion thereof, substrate heating is controlled in such a manner as to maintain the temperature of its exposed surfaces at a value that is no greater than the minimum temperature for the reaction gas to deposit the material that is to be infiltrated, while portions of the substrate that are remote from its exposed surfaces are at a temperature that is greater than the minimum temperature for deposition.